Banknotes and like securities are commonly produced in the form of individual sheets (or successive portions of a continuous web which are ultimately cut into sheets) each carrying a plurality of individual imprints arranged in a matrix of rows and columns, which sheets are subjected to various printing and processing steps before being cut into individual notes. Among the printing and processing steps typically carried out during the production of banknotes are offset printing, intaglio printing, silk-screen printing, foil application, letterpress printing and/or varnishing. Other processing steps might be carried out during the production such as window cutting, ink-jet marking, laser marking, micro-perforation, etc. Once fully printed, the sheets have to be subjected to a so-called finishing process wherein the sheets are processed, i.e. cut and assembled, to form note bundles and packs of note bundles.
Banknotes and like securities further have to typically meet strict quality requirements, especially concerning the printing quality thereof. Therefore, during the course of their production, banknotes or securities are typically inspected in order to detect, and advantageously mark, defective notes, i.e. notes exhibiting a low printing quality, printing errors, physical damages and the like, such that these defective notes can be sorted out. Inspection can be carried out at various stages of the production, manually, on-line on the printing or processing presses, and/or off-line on dedicated inspection machines. Final inspection of the banknotes is conveniently carried out prior to finishing as this will be explained hereinafter in reference to FIG. 1 which is illustrative of the prior art.
FIG. 1 summarizes a typical process of producing securities wherein a final inspection step is carried out prior to finishing. The production process illustrated in FIG. 1 is advantageous in that it enables maximisation of the production efficiency by reducing waste to a minimum and enables the production of note bundles and packs of note bundles with uninterrupted numbering sequence.
Step 501 in FIG. 1 denotes the various printing phases which are typically carried out during the production of securities. As mentioned, these various printing phases include in particular an offset printing phase whereby sheets of securities are printed on one or both sides with an offset background, an intaglio printing phase whereby the sheets are printed on one or both sides with intaglio features (i.e. embossed/relief features which are readily recognizable by touch), a silk-screen printing phase whereby the sheets are printed on one or both sides with silk-screen features, such as features made of optically variable ink (OVI), and/or a foil/patch application phase whereby foils or patches, in particular so-called optically variable devices (OVD), holograms, or similar optically diffractive structures, are applied onto one or both sides of the sheets, etc.
As a result of the various printing phases of step 501, successive sheets S are produced. While quality control checks are usually performed at various stages during the production of the securities, a final quality check is typically carried out on the full sheets S after these have been completely printed. This full-sheet quality inspection is schematised by step 502 in FIG. 1. Three categories of sheets in terms of quality requirements are generated as a result of this full-sheet quality inspection, namely (i) entirely good sheets S0 (i.e. sheets carrying imprints which are all regarded to be satisfactory from the point of view of the quality requirements), (ii) partially defective sheets S′ (i.e. sheets carrying a mixtures of imprints which are satisfactory from the point of view of the quality requirements and imprints which are unacceptable, which defective imprints are typically provided with a distinct cancellation mark), and (iii) entirely defective sheets SX carrying only defective imprints. From this point onward, the three categories of sheets follow distinct routes. More precisely, the entirely defective sheets SX are destroyed at step 510, while the entirely good sheets S0 are processed at steps 503 to 505 and the partially defective sheets S′ are processed at steps 520 to 523.
Referring to steps 503 to 505, the entirely good sheets S0 are typically numbered at step 503, then optionally varnished at step 504, and finally cut and subjected to an ultimate finishing process at step 505, i.e. stacks of sheets S are cut into individual bundles of securities (such as banknote bundles) 200, which bundles 200 are typically banderoled (i.e. surrounded with a securing band) and then stacked to form packs of bundles 210. While the sheets S are processed in succession at steps 503 and 504, step 505 is usually carried out on stacks of hundred sheets each, thereby producing successive note bundles 200 of hundred securities each, which note bundles 200 are stacked to form e.g. packs 210 of ten note bundles each.
Referring to steps 520 to 523, the partially defective sheets S′ are firstly cut into individual notes at step 520 and the resulting securities are then sorted out at step 521 (based on the presence or absence of the cancellation mark previously applied on the defective imprints at step 502), the defective notes being destroyed at step 510, while the good notes are further processed at steps 522 and 523. At step 522, the individual securities are numbered in succession and subsequently subjected to a finishing process at step 523 which is similar to that carried out at step 505, i.e. note bundles of securities 200 are formed, which note bundles 200 are banderoled and then stacked to form packs of note bundles 210.
As regards the varnishing operation, FIG. 1 shows that such varnishing is typically carried out on full sheets at step 504 after full-sheet numbering at step 503. While this varnishing step is preferred, it is not as such required. Varnishing may furthermore be carried out at a different stage of the production, for example before full-sheet inspection at step 502 or immediately after full-sheet inspection at step 502, on the entirely good sheets S0 and partially defective sheets S′ (which other solution would imply that numbering is carried out after varnishing).
In case keeping the numbering sequence throughout the notes of successive bundles 200 is not required, the partially defective sheets S′ could follow a somewhat similar route as the entirely good sheets S0, i.e. be subjected to a full-sheet numbering step (thereby numbering both the good and defective imprints), then to full-sheet varnishing, before being cut into individual securities, sorted out to extract and destroy the defective securities, and then subjected to an ultimate finishing process to form note bundles and packs of note bundles (in this case single-note numbering would not be required).
In all of the above instances, the entirely good sheets S0 and the partially defective sheets S′ follow distinct routes and are numbered in separate numbering processes. This may create logistical problems in that the entirely good sheets S0 and the partially defective sheets S′ have to be routed to different locations and handled differently and separately.
European Patent Publication EP 1 808 391 A1 discloses, with reference to FIGS. 7A-7E thereof, a sheet numbering process whereby sheets carrying a plurality of imprints that are arranged in a matrix of rows and columns are first inspected with a view to identify specific groups of partly defective sheets where defects are concentrating within single columns of imprints and sorting these sheets in dependence of the relevant column where the defects are located Once sorted, the relevant sheets are numbered by causing the relevant numbering and imprinting machine to omit numbering in the individual columns where one or more defects have been identified or by removing the corresponding numbering devices from the numbering and imprinting machine.
A considerable disadvantage of this known process resides in the fact that it requires a complex sorting operation prior to the numbering operation. A further disadvantage of this known process resides in the fact that imprints that are not considered to be defective but that happen to be located within the same column where a defect is detected are not at all numbered, thus generating unnecessary waste. Furthermore, the process of EP 1 808 391 A1 requires individual and separate numbering of each specific group of partly defective sheets in dependence of the sorting of the sheets. This numbering is carried out on a separate numbering and imprinting machine which is pre-set in dependence of the relevant group of partly defective sheets to be numbered (namely by turning off or removing the relevant numbering devices) prior to undertaking the numbering operation.
There is therefore a need for an improved process of numbering sheets, and a sheet-processing machine enabling the same, which simplifies logistics as far as numbering of the sheets is concerned. There is furthermore a need for such an improved process of numbering sheets (and related sheet-processing machine) that is more flexible than the known solutions.